Rates of thrust faulting at the front of the Precordillera in western Argentina: Implications for the seismic hazard in Mendoza city from surface expose dating and paleoseismology

目前纳斯卡板块和南美板块之间的大部分板块会聚都发生在安第斯山脉的弧后地区。在北纬28°S和33.5°S之间，许多历史上的板内大地震证明，持续的形变集中在前纪的前部和更东边的帕姆花生山脉的基底隆起上。前纪山前活动逆冲断层的长期滑动速率尚不清楚，尽管这些断层对前纪前山前的主要城市构成了严重威胁。在门多萨市附近的两条地表冲断断层上，我们将结合地貌测绘、地形测量、构造错动的河流阶地暴露年龄、古地震调查和发光测年，以确定(1)垂直抬升和水平缩短的长期速率和(2)这些断层过去发生破坏性地震的频率。将长期缩短率与从GPS数据(~5 mm/a)推断的短期速度进行比较，将为了解断层速率的时间变化，即地震频率的变化提供重要的洞察。计划中的调查将有助于更好地限制前纪元时代前部的地壳变形，从而更好地控制门多萨市的地震危险。

A significant amount of the current plate convergence between the Nazca and the South American Plate is taken up in the back-arc region of the Andes. Between latitude 28°S and 33.5°S many large historical intraplate earthquakes document that ongoing deformation is concentrated along the front of the Precordillera and the basement uplifts of the Sierra Pampeanas farther east. Long-term slip rates of active thrust faults at the mountain front of the Precordillera are not known, although these faults pose a serious threat to major cities at the front of the Precordillera. At two surface-breaking thrusts near Mendoza city we will combine geomorphic mapping, topographic surveying, exposure dating of tectonically offset river terraces, paleoseismologic investigations, and luminescence dating in order to determine (1) the long-term rates of vertical uplift and horizontal shortening and (2) the frequency of destructive earthquakes on these faults in the past. Comparison of the longterm shortening rates with short-term velocities inferred from GPS data (~5 mm/a) will provide important insight into temporal variations in the rate of faulting, i.e. changes in the frequency of earthquakes. The planned investigations will help to better constrain crustal deformation at the front of the Precordillera and thus the seismic hazard for Mendoza city.